The present applicants were co-inventors of previous patent applications relating to novel spiro-oxathiolane/quinuclidine compounds, see e.g. European patent application No. 0205247 A2, published Dec. 17, 1986, based on Israel patent applications Nos. 75166 dated May 10, 1985 and 77568 dated Jan. 10, 1986, and commonly assigned U.S. patent application Ser. No. 853,404 filed Apr. 18, 1986, the contents of which are incorporated herein by reference. These novel compounds were found to possess central nervous system activity. The biological activity of the compound 2-methylspiro(1,3-oxathiolane-5',3)quinuclidine, which exists as geometrical cis-and trans-isomers depending upon whether the 2-methyl group is located on the same side of the oxathiolane ring as the quinuclidine ring nitrogen atom (cis) or on the other side of the quinuclidine ring nitrogen atom (trans), was in particular extensively investigated, and it was found on the basis of preclinical tests that the cis- compound could be especially promising for the control of senile dementia of Alzheimer's type (SDAT).
It is a principal object of the invention to provide novel spiro-oxathiolane/quinuclidine compounds, which bear a close structural relationship to the compounds disclosed and claimed in the aforementioned prior patent applications, but which are nevertheless clearly distinguished therefrom. Further objects of the invention, and especially those which relate to the provision of useful pharmaceutical compositions and methods for the treatment of disease in mammals, will be apparent from the description which follows.